1. Field of the Invention
The present invention relates generally to dollies, hand trucks, and other devices designed to aid in the lifting and transport of small loads. The present invention relates more specifically to dollies, hand trucks, and other such devices that are capable of vertically elevating a load prior to its being transported.
2. Description of Related Art
The transport of small to medium sized loads from one place to another within a localized area has heretofore generally been accomplished by means of simple two wheeled vehicles referred to as dollies or hand trucks. Larger loads which require transportation within similar confines more frequently are handled on pallets by pallet moving equipment, either hand operated or motor driven. Hand trucks and dollies are utilized in preference to such devices designed for larger loads because of their smaller size and their resultant maneuverability and control.
Specialized hand trucks and dollies have been developed for specific applications for everything from transporting large barrels to moving household appliances. Most dollies and hand trucks, however, share the same basic functional characteristics Dollies are generally two wheeled, have a lifting plate or platform, and provide a handle/leverage means for lifting and controlling the load. An important functional feature of most dollies and hand trucks is their capacity to place their load platform under a load, in its position on the ground or floor, and then lift the load so that it is no longer in contact with the ground, but is supported by the frame of the dolly or hand truck. The load is then transportable across the ground or floor surface by use of the wheels on the vehicle frame.
The simplest means for achieving this most basic function of lifting a load in an efficient manner is through the use of a lever mechanism that uses the wheel axle as a fulcrum point. A lever mechanism, therefore, allows the mover to multiply the force of his lifting effort by way of a rotational torque about the fulcrum point of the lever. The typical dolly or hand truck utilizes a relatively short lift platform and a relatively long handle assembly so as to impart the necessary force multiplying factor to the mover's efforts.
The problems, however, with this simple means of achieving a combination of wheeled transport and force multiplying lever function, are numerous. The first and most obvious problem is the instability of the load and the moving device, once the load has been lifted for transport. In most hand trucks, there is no stable transport position that does not rely upon the constant control and effort of the individual doing the moving. This instability is a result of combining the fulcrum point of the lever mechanism with the axle point of the wheel assembly. While this makes for a simple overall mechanism, it means that the operator is tied to control of the hand truck when it is in a transport configuration.
A second, but no less troublesome, problem becomes apparent with loads that do not lend themselves to be tilted during loading or transport. Integral with the above described combined function of the lever means and the wheel assembly, is the necessity that the load be rotated to some extent about the fulcrum point of the lever. Since the load platform is typically in a fixed relationship with the handle/lever means, it will necessarily be disturbed from its initial horizontal position upon loading, to an angled positioned upon transport. This angled position could be anywhere from a few degrees from the horizontal to a nearly vertical position, depending upon the capability of the mover to control the lever arm. In any case, there are many types of loads that can not be subjected to this rotational displacement, either because of an internal instability or because of an external instability that results from the stacking of a number of individual loads. Whatever the reason, there are many items, both in industrial applications and in household situations, that can not or should not be tilted during transport.
There have been some efforts to attempt a stable and efficient means of transport for such objects. Some of these efforts have focussed on the size and/or weight of the object being moved and the inability of the mover to constantly support the load, even with a lever arrangement, during transport. Some of these efforts have focussed on the capacity to raise and transport the load without tilting. Most of these efforts suffer from problems of complexity, size, and the resultant costs that complexity and size demand. Those that attempt to remain simple and less costly, tend to suffer from a lack of structural integrity.
There is a need, therefore, for a simple yet effective means for transporting small to medium sized loads, in both industrial and household situations, that provides both transport stability and the capacity to lift the loads without rotationally displacing them from their ordinary stance. Examples of loads that might benefit from such a device include large plants, office supplies, books, barrels, and industrial supplies, to name a few.